Domestic clothes dryers are a common household appliance that, in conjunction with domestic washers, have reduced the burden of laundry on many households by reducing the amount of time devoted by household caregivers to washing and drying clothes. Such clothes dryers typically include a housing (also known as a bulkhead) and a rotating drum, or cylinder, supported within the housing. Commercially available air vented domestic clothes dryers use the rotating drum to tumble loads of washed clothes in a heated environment by generally using a blower/fan to pull ambient air across heater coils to raise the temperature of air passing into the drum. The heated air is pulled through the tumbling clothes and out through a lint screen for discharge. Commercially available condensing domestic clothes dryers also use the rotating cylinder to tumble loads of laundry in a heat environment, but treat the air in a slightly different manner. These condensing domestic clothes dryers use a blower/fan to pull ambient air across heater coils into the drum, through the tumbling clothes and out through a lint screen, across a condenser coil to remove moisture, and then return to the drum.
Both types of dryers use dryer seals to support and seal the drum usually at both ends. These dryer seals perform a multitude of functions within these domestic clothes dryers. Current seals are made with felt nonwoven materials produced with varying percentages of wool and polyester and also on occasions the addition of vinyl or some low friction material. In particular, these seals are usually in the form of rings of felt which may be disposed between the housing and the drum so as to bear against the drum as it rotates. The materials of the ring can interact to form an elastic fit or may be glued into position depending on the arrangement of components.
The seals serve as a friction surface between the rotating drum and the bulkhead sections while also maintaining a seal to hold drying heat within the drum. In particular, the use of seals is desirable to reduce the friction, or prevent the creation of excess friction, between the drum and the bulkhead and to prevent air leakage between the drum and the clothes dryer cabinet which could detrimentally affect the air flow system of the dryer.
The structure of the seals can vary depending on the type, commercial brand and design of the dryer. Many current seals have multi-layered ring structures incorporating a folded over exterior layer such as wool-blend, polyester, rayon, aramid fibers or polyester blend nonwoven material. These multi-layered ring structured seals can be folded and stitched to assume different shapes to perform their intended functions within an appropriate dryer design. In some embodiments, a spacer material such as polyester or polyester blend material can also be included that can be held within the folded over exterior. The folded materials can form legs that project outwardly from the folded edge. These legs can have a sealing contacting relationship with the rotating drum. In such seal embodiments, the spacer material can typically be held in place by two seams with a first positioning seam running between an upper edge of the spacer material and one side of the folded over exterior and a second holding seam extending at an inboard position through all three layers so as to establish a coordinated stable structure.
Despite their widespread use in U.S. homes, clothes dryers are involved in a significant number of residential fires. According to some estimates, dryer fires produce annual U.S. property losses approaching $100 million, and lead to multiple consumer deaths and hundreds of injuries. Proper installation and effective maintenance of clothes dryers can significantly reduce the risk of appliance-related fires. But recent research has shown that product construction and design considerations are also important elements in building safer dryers.
The causes of electric dryer fires have been extensively researched over the past decade by the U.S. Consumer Product Safety Commission (CPSC), industry associations including the Association of Home Appliance Manufacturers (AHAM), individual appliance manufacturers, and standards organizations including Underwriters Laboratories (UL). Some research has pointed to the accumulation of lint and the subsequent reduction of air flow as a primary cause of dryer fires. Yet, other testing has supported claims that the cause of dryer fires can be attributed to a number of factors. In particular, studies have found that factors such as a dryer load, a dryer's electrical system, and a dryer's mechanical system also played a major role in reported dryer fires.
While increased consumer education regarding risks with dryer use can help reduce the number of dryer fires, attention should be focused on the design of dryers themselves and the ability of a dryer unit to actually contain a fire should one occur. United States (U.S.) fire regulations have been defined by UL Appliance Containment #UL 2158, which requires that a fire in the appliance be contained within the appliance and not allowed to escape into the environment surrounding the appliance. For fires that initiate inside the drum of a clothes dryer, one potential point of egress is the mating area between the cylinder and the front door and/or rear bulkhead. Clothes dryer fires have a wide temperature range depending on the fuel value of the load plus any fuel value items in the unit construction such as plastic baffles, friction reducing rings, fittings or bulkhead components, etc. The temperatures have been tested to exceed 1300° F. and cycle between low and high values. These temperatures exceed the capability of sustaining structural integrity of traditionally used wool and polyester nonwoven materials, even FR treated polyesters.
Another serious and dangerous situation that arises when a fire starts or begins to smolder within the drum is the opportunity of a smoke explosion. A smoke explosion is a condition whereby the rapid increase in pressure inside the drum/combustion chamber during a dryer fire is sufficient to overcome the door lock mechanism. The lock specification has been tested and indicated a twelve (12) foot pounds locking force. Therefore, these smoke explosions create a great release of force that can create opportunity for bodily injury to people in the vicinity of the dryer and can cause the fire to spread quickly from being contained in the dryer to area surrounding the dryer and to other parts of the house. These smoke explosions occur when a fire is contained in the drum producing smoke and providing a spark. Tests have shown that, as fire burns, the right mixture of carbon monoxide (CO) from the white smoke, which contains residual unburnt hydrocarbons, and oxygen (O2) can occur within drum. The fire ignites this deadly mixture once it is achieved to explosive and horrific effect. Such a condition is known as pyrolysis.
As such, a need exists for improved dryer seals that can help reduce the opportunity of smoke explosions within dryers and that can help contain fires that initiate inside of a drum of a clothes dryer.